A little of topic but if the stem area is packing with dirt/debris, you may be able to get some plastic push on caps from a hardware store or specialty automotive store. Makes for a nice clean look as well! If not, I've also seen people fill that void with black silicone. Just swipe it with your finger while the silicone is still wet for a flush smooth appearance. When you need to get to the lock nuts just scoop the dried silicone out with a pic or small flat head screw driver.
